1. Field of the Invention
The invention relates to a grinding machine and a grinding method.
2. Description of the Related Art
Japanese Patent Application Publication No. 2000-218479 describes that, in external cylindrical grinding, the roundness of a workpiece is measured, a correction value is derived from a roundness error, and the workpiece is ground with a correction. In the case of grinding a crankpin, the degree of deflection of the crankpin varies because the stiffness of the crankpin varies depending on the rotational phase of a crankshaft. Therefore, Japanese Patent Application Publication No. 2000-107902 and Japanese Patent Application Publication No. 11-90800 each describe deriving a correction value based on the degree of deflection of a crankpin depending on the rotational phase a crankshaft and performing grinding with a correction. Thus, it is possible to achieve a high degree of accuracy of the roundness of the crankpin.
However, even if variations in the degree of deflection of the crankpin due to variations in the stiffness of the crankpin depending on the rotational phase of the crankshaft are taken into account, there is still room for improvement in the degree of accuracy of the roundness of the crankpin.